There are well known various painting methods of spraying articles or objects with different color paints by the use of a paint spray gun. Apparatuses embodying such a painting method incorporate a color paint exchanging device which exchanges paints to be sprayed from one color to another and alternately supply air and cleaning thinner to the paint spray gun.
In the painting method, after the preceding painting and before spraying another article or object with another color of paint, cleaning thinner is discharged into a pipe between the color paint exchanging device to the spray gun so as to wash off and completely remove the preceding paint remaining in the pipe and, thereafter, the another color of paint is allowed to flow into the pipe. One objective desired with such painting methods using a cleaning thinner is to keep the waste of paint small.
In an attempt at eliminating the loss of paint, disclosed in, for example, Japanese Patent Unexamined Publication No. 60-61,076 entitled "Painting Method", filed on Sept. 13, 1983 and laid open on Apr. 8, 1985, is an improved painting method in which, at a predetermined time before the completion of the preceding painting, the paint for the preceding painting is cut off and the cleaning thinner is discharged to force out the paint remaining in the pipe so as to continuously spray the paint at a same rate as before being cut off.
Describing in more detail, the process of the painting method comprises at least a preceding painting step to spray an object with a color paint, a continuous preceding painting step to continuously spray the same object with the color paint which is forced out by thinner, a cleaning step in which air and thinner are alternately repeatedly discharged to wash off the pipe between the color paint exchanging device and the spray gun, and a step to discharge another color paint and spray another object with the another color paint.